This invention relates to a system which includes a reader and a transponder displaced from the reader for identifying the transponder to the reader in accordance with a code individual to the transponder and transmitted to the reader at the command of the reader. The system is able to provide such identification without interference from extraneous noise, even at high levels, or small obstacles in the path of data transmission between the transponder and the reader. More particularly, the invention relates to a system for initially transmitting an identifying code from the reader to the transponder and programming this code into the transponder to identify the transponder.
As our society becomes increasingly complex, it becomes increasingly important to be able to identify different objects. For example, in an aircraft plant for manufacturing a jet airplane, thousands, and even tens of thousands, of different tools are required to manufacture the different parts incorporated into the airplane. It is accordingly important to be able to identify the individual tools quickly and reliably. One reason is that a fast and reliable identification of each individual tool is cost-efficient because it minimizes the time needed to identify such tool. Another reason is that a fast and reliable identification of each individual tool minimizes the possibility that the wrong tool will be selected and used on a workpiece, thereby causing the workpiece to be ruined or damaged.
It has been known for an extended period of time that it would be desirable to provide a system for obtaining a fast and reliable indication of objects such as tools. An extensive effort has accordingly been made by a wide variety of different parties to provide a satisfactory system. Such efforts have not been productive for a number of reasons. As a result, a satisfactory system still does not exist for identifying objects such as tools.
The systems now in use are undesirable for a number of reasons. They are not fast. For example, some of the systems use a transponder which stores energy received from a displaced reader and which then generates a code after such storage of energy. The energy is stored by charging a capacitance at the transponder. Other systems sweep a range of frequencies and detect the perturbations produced at individual frequencies in such frequency range. As will be appreciated, both types of systems are relatively slow.
The systems now in use have other severe limitations. The systems are not self synchronous. In other words, the systems do not operate on the basis of clock signals internally generated in the system. As a result, the systems sometimes provide the reader with false and inaccurate indications of the code identifying the object at the transponder. This causes an improper object to be identified sometimes at the reader.
The systems now in use also have other critical limitations. For example, the systems now in use are sometimes responsive to extraneous signals. Furthermore, in the systems now in use, members in the path between the transponder and the reader sometimes block the reception by the reader of the identifying signals transmitted by the transponder. This blockage has occurred even when the members in the path are relatively small. These problems have been exacerbated by the fact that the systems now in use are not self-synchronous. This has caused the systems now in use to identify objects improperly.
The systems now in use are also relatively complicated. This has caused the systems now in use to be excessively large from the standpoint of the space occupied by such systems. It has also prevented the systems now in use from taking advantage of integrated circuit technology. For example, it would be desirable to dispose the transponder on a single integrated circuit chip and to dispose all, or at least substantially all, of the reader components on another integrated circuit chip.
Co-pending application Ser. No. 840,318 relating to an "Identification System" filed by me on Mar. 14, 1986, now U.S. Pat. No. 4,752,776 and assigned for record to the assignee of record in this application discloses and claims a system which overcomes the above disadvantages. The system is fast, accurate and reliable. It operates on a self-synchronous and passive basis. It is immune to extraneous signals and it is effective even when small members are disposed between the transponder and the reader. It is simple and compact such that the transponder is disposed on a single integrated circuit chip and all, or substantially all, of the reader circuit is disposed on another single integrated circuit chip. It is quite tolerant of variations in the values of components so that it can be produced economically in quantity.
In one embodiment of the system disclosed and claimed in co-pending application Ser. No. 840,318, a reader (which can also be considered to be an interrogator) identifies information, such as the identity of an object at a transponder, provided in binary form at the transponder. The reader initially generates a pulse which activates the transponder into transmitting a series of signals, such as by magnetic induction, to the reader. Upon each count of a particular number of signals in the reader, the reader generates a new pulse which causes the transponder to produce a new series of signals. The generation of the pulses by the reader may occur through the charge. and discharge of energy in a storage member such as a capacitance.
The series of signals produced by the transponder in co-pending application Ser. No. 840,318, U.S. Pat. No. 4,752,776, may have erther a first frequency or second frequency. The signals may be generated at the first and second frequencies in each sequence in an order dependent upon (a) the binary code provided at the transponder and (b) the polarity of the pulse produced by the reader in such sequence. The signals may be generated at the second frequency by connecting a capacitance across a coupling coil at the transponder. The reader then identifies the information by demodulating the signals received by it at the first and second frequencies.
The reader in co-pending application Ser. No. 840,318 is able to interrupt at any time the generation of the sequences of signals at the transponder when it does not receive the signals transmitted by the transponder. The reader then operates on a free running basis to generate pulses of opposite polarity at a relatively low frequency. In this way, the reader is constantly prepared to activate the transponder when the transponder becomes subsequently disposed within the effective range of the reader.
The memory storing the code in the transponder may be programmable. This invention provides a system operable at the reader for programming a binary code into such memory from the reader to constitute the binary information thereafter identifying the object. The code is transmitted from the reader to the object by sequences of pulses similar to the pulses described above as being transmitted from the reader to the transponder to interrogate the transponder as to the code in the transponder.
To program the memory with such a code, the reader in this invention generates, and transmits to the transponder, sequences of pulses, each sequence coding for a programmable item of information (e.g. binary "1", binary "0" and reset). Depending upon the individual programmable item, the coded sequence may have pulses of the same polarity or pulses of opposite polarity At a time related to each each such sequence, the reader produces a sequence different from the coded sequence and indicating that pulses coding for a programmable item follow.
The transponder in this invention demodulates and decodes the transmitted pulses to to recover the identifying code. This code is then recorded in the programmable memory and is used thereafter to identify the transponder when the reader interrogates the transponder as described above.